// File: ex7-15a.cpp - Abstract classes and Polymorphism

#include <iostream>
#include <iomanip>
#include <cmath>
#include <ctime>
#include <cstdlib>
#include <string>
using namespace std;

const double pi = 3.141592654;

double drand();

class Shape
{
protected:
    double x;
    double y;
public:
    Shape(double, double);
    // pure virtual functions
    virtual double area(void) const = 0;
    virtual double girth(void) const = 0;
    virtual string type() const = 0;
    virtual ~Shape() {}
    static const int NumShapeType = 3;

    enum ShapeType
    {
        Square, Triangle, Circle
    };
    friend ostream& operator<<(ostream& out, const Shape& shape);
};

Shape::Shape(double c_x, double c_y) : x(c_x), y(c_y)
{
}

ostream& operator<<(ostream& out, const Shape& shape)
{
    out << setprecision(2) << fixed;
    out << shape.type() << " (" << shape.x << ',' << shape.y << ")  ";
    out << "area=" << shape.area() << "  girth=" << shape.girth();
    return out;
}

class Square : public Shape
{
private:
    double side;
public:
    Square(double c_x, double c_y, double s);
    double area(void) const;
    double girth(void) const;

    string type() const
    {
        return "Square";
    }
};

Square::Square(double c_x, double c_y, double s) : Shape(c_x, c_y), side(s)
{
}

double Square::area(void) const
{
    return side * side;
}

double Square::girth(void) const
{
    return 4. * side;
}

class Triangle : public Shape
{
private:
    double a, b, c; // length of 3 sides
public:
    Triangle(double c_x, double c_y, double s1, double s2, double s3);
    double area(void) const;
    double girth(void) const;

    string type() const
    {
        return "Triangle";
    }
};

Triangle::Triangle(double c_x, double c_y, double s1, double s2, double s3)
: Shape(c_x, c_y), a(s1), b(s2), c(s3)
{
}

double Triangle::area(void) const
{
    double s = (a + b + c) / 2.; // semiperimeter
    return sqrt(s * (s - a)*(s - b)*(s - c));
}

double Triangle::girth(void) const
{
    return a + b + c;
}

class Circle : public Shape
{
private:
    double radius;
public:
    Circle(double c_x, double c_y, double r);
    double area(void) const;
    double girth(void) const;

    string type() const
    {
        return "Circle";
    }
};

Circle::Circle(double c_x, double c_y, double r) : Shape(c_x, c_y)
{
    radius = r;
}

double Circle::area(void) const
{
    return pi * radius*radius;
}

double Circle::girth(void) const
{
    return 2. * pi*radius;
}

int main()
{
    srand(time(0));
    Shape* ptrShape;

    // Create 10 shapes
    for (int i = 0; i < 10; i++) {
        Shape::ShapeType randomShape = static_cast<Shape::ShapeType> (rand() % Shape::NumShapeType);
        switch (randomShape) {
            case (Shape::Circle):
                ptrShape = new Circle(drand(), drand(), drand());
                break;
            case (Shape::Square):
                ptrShape = new Square(drand(), drand(), drand());
                break;
            case (Shape::Triangle):
                ptrShape = new Triangle(drand(), drand(), drand(), drand(), drand());
                break;
            default:
                ;
        }
        cout << *ptrShape << endl;
        delete ptrShape;
    }
}

double drand()
{
    return (rand() + 1.0) / (rand() / 10.0);
}



*****  OUTPUT  *****

Triangle (11.29,12.37)  area=nan  girth=27.49
Square (12.12,10.87)  area=56.15  girth=29.97
Square (9.06,13.19)  area=49.80  girth=28.23
Triangle (5.38,7.97)  area=5.37  girth=15.11
Square (22.44,6.95)  area=1844.48  girth=171.79
Circle (1.63,0.90)  area=16.02  girth=14.19
Circle (57.05,0.42)  area=467.19  girth=76.62
Square (12.33,5.10)  area=5.44  girth=9.33
Square (3.97,96.71)  area=143.86  girth=47.98
Triangle (6.31,1.05)  area=17.93  girth=20.79